Method of reducing the viscosity of nitrocellulose



May 6, 1930. Hv TO IER 1,757,491

METHOD OF REDUCING THE VISCOSITY OF NITROCELLULOSE Filed Nov. 1926 A/ITQOCi'L L JLOS I NVEgVTOR, George H. 105161, BY ny AiTORNEYS.

Patented llllay h, 193% GEORGE HQTOZIER, OF ROCHESTER, NEW YORK, ASSIGNOR T0 EASTMAN KODAK COM- PANY, O15 ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK Application filed November 6, 1926. Serial No. 146,668.

This invention relates to the reduction of the viscosity of nitrocellulose. This is accomplished by boiling in water at a pressure greater than atmospheric. During the process, which is carried on in an autoclave, the nitrocellulose is maintained entirely submerged in the water. Steam is introduced near the bottom of the autoclave and beneath the water level, which is determined by the height of an outlet near the upper part and connected to a steam trap. Under such treatment, the viscosity is lowered to a marked degree and the keeping of the nitrocellulose covered constitutes a valuable safety precaution.

The method of carrying out the process will be more clearly understood by reference to the accompanying drawing, in the single figure of which there is a formal showing of the apparatus used, the-kettle being shown in section.

A pressure kettle of any desired type may be used. In the form illustrated, it consists of upper and lower flanged sections 1 and 2 connected by bolts 3 with a removable cover 4 held by bolts 5 over the loading opening 6. At the bottom is an unloading nozzle 7 controlled by slide 12. On one side of the kettle is an .voutlet 8 and below the level of the outlet Sis an inlet 9 through which live steam is supp led from a suitable source, not shown,

being controlled by valve 10. The kettle is jacketed with a heat insulating layer 11.

The outlet 8 is connected to a steam trap 13, of any approved form, by which condensed water is withdrawn without allowing the steam to escape, there being in the connection, a heat interchanger ltwhich is useful in especially economical operation, the heated coil 21 being connected by tubes 22 to a boiler or the like. i v

The interior of the kettle has an acid resistant lining 15 which may be of any suitable material, such as chromium steel, a suitable bronze, aluminum, durion, chromium plated steel. or an acid resistant tile, such as is used in sulphite pulp digesters, the last named being preferred.

I have found a maintained temperature of 125 C. to give very satisfactory results but contemplate any temperature above 110 C. The upper useful range would be determined by the practical limitations of the apparatus.

The liquid may be circulated by means of a pump 15', passing through an outlet 16 from the tank, and a heater 16 back to the inlet 17'. Fresh, hot water under pressure may be injected into the system at any point, as by injector valve 18, and this may be used to fill the kettle and also to rinse the nitrocellulose, before, after or during cooking.

An amount of nitrocellulose 19 such as will be completely immersed in the water, the level 20 of which will be determined'by the water outlet 8,'is placed in the kettle. Live steam is introduced at a high temperature, say 140, below this water line, through the inlet9, at

igh tempe'rature'and pressure. After the contents are heated to the desired temperature, only a small flow of steam is required to maintain this temperature and to replace the acidified water drawn ofi'. Fresh hot water may be introduced through the valve 18; the water in the kettle may be circulated by means of the pump15. The acidity develo s slowly and the withdrawal of the hot acidi ed water at outlet 8 is correspondingly slow. While the heat loss due to this slow withdrawal is not excessive, the heat interchanger will prove economical.

The treatment is maintained until the desired viscosity is attained. Whilethis would, of course, be dependent in part upon the particular materials and conditions employed, I have found a period of 8 to 24 hours under the conditions described to be suiiicient.

If a relatively large amount of hot water is introduced through 18 during cooking, sutlicient to keep the water clear of practically all decomposition products as they are formed, a correspondingly greater amount of steam will necessarily be used to maintain the temperature, and there will be a greater flow of water from outlet 8. In this case, little, if

any, washing is necessary when the treatment is ended and, sincethe water is kept substantially free from acid during the treatment, the necessity for an acid resistant lining is obviated.

The maintenance of the level is a vital point of my im rovement. The steam trap permits the with rawal of the condensate as it forms without reduction of the pressure, and the conditions of treatment are thus maintained uniform, under control at all times and the nitrocellulose iskept covered.

I contemplate as included in my invention such modifications and equivalents as fall 'Within the scope of the appended claims.

, tion containing a standard amount of nitrocellulose.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is The process of reducing the viscosity of nitrocellulose thatcomprises completely immersing a quantity of nitrocellulose in water in a closed vessel, introducing super-heated steam under pressure below the water level during the continuance of the process, maintaining the contents of the vessel under high temperature and pressure conditions and at the same time throughout the process withdrawing any excessfof water including any products of decomposition whereby the nitrocellulose is constantly and completely immersed in water at a constant level under high temperature and'pressure conditions.

2. The recess of reducing the viscosity of nitrocellulose that comprises completely immersing a quantity of nitrocellulose in water in a closed vessel, introducing superheated steam under pressure below the water level, maintaining the contents of the vessel at a temperature above 110 C. under pressure andv at the same time withdrawing any excess of water including any products of decomposi-' tion, whereby the nitrocellulose is constantly and completely immersed in water at a constant"level and at a temperature exceeding 110 C.

3. The process of reducin the viscosity of nitrocellulose that comprises completely immersing a quantity of nitrocellulose in water in a closed vessel, maintaining the contents of the vessel at-a temperature of at least 110? C. and under pressure for at least eight hours, introducing superheated steam under pressure below the water level continuously throughout such period and at the same time continuously withdrawing any water in excess of that in which the nitrocellulose was originally immersed, whereb the nitrocellulose is constantly and comp etely immersed in water under high temperature and pres sure conditions for at least eight hours and whereby the products of decomposition are,

at least in part, continuously removed during such period.

4. The process of reducing the viscosity of nitrocellulose which comprises completely imhigh temperature and pressure conditions,

circulating the water in the vessel and withdrawin any excess of water, whereby the nitrocel ulose is constantly and completely immersed in water under high temperature and pressure conditions and the products of decomposition are, at least in part, continuously removed.

5. The process om reducing the viscosity of nitrocellulose which comprises completely immersing a quantity of nitrocellulose in water in a closed vessel, introducing superheated steam under ressure below the water level maintaining t e contents of the vessel under high temperature and pressure conditions, adding occasional water to the system, circulating the water in the vessel and withdrawing any excess of water, whereby the nitrocellulose is constantly and completely immersed in Water underhigh temperature and pressure conditions and the products of decomposition are, at least in part, continuously removed.

Signed at Rochester this 27th day of October I926.

GEORGE H. TOZIER. 

